SOUND

 The vibrations travel through the air or another medium (solid, liquid or gas) to the ear. The stronger the vibrations, the louder the sound. 

SOUND TRAVELS IN ALL DIRECTIONS

You can reflect a sound wave off something the same way light will reflect off a mirror or water waves will bounce off a sea wall and go back out to sea. Stand some distance from a large flat wall and clap your hands repeatedly. Almost immediately you'll hear a ghostly repeat of your clapping. What you hear is, of course, sound reflection, better known as an ECHO

Sonar

Sonar (sound navigation and ranging) is a technology that uses acoustical waves to sense the location of objects in the ocean.

Ultrasound

An ultrasound scan is a medical test that uses high-frequency sound waves to capture live images from the inside of your body